Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:
ASNaccess service networkBSbase stationCSNconnectivity service networkDCDdownlink channel descriptor (holds parameters that terminals need to begin communicating with base station)DLdownlink (BS to terminal)IDidentifierIPinternet protocolMACmedium access controlNAPnetwork access provider (a company owning base stations and providing access to NSP(s))NSPnetwork service provider (a company owning “core” network, which provides access to internet)SII-ADVsystem identity information advertisement (message)UCDuplink channel descriptor (holds parameters that terminals need to begin communicating with base station)ULuplink (terminal to BS)WiMAXworldwide interoperability for microwave access
WiMAX is a name given to a set of technologies sponsored by the WiMAX Forum. WiMAX was originally designed to provide a wireless alternative to broadband cable connections. Originally WiMAX was only able to operate with fixed or nomadic terminals, as handovers from cell to cell were not supported. WiMAX has subsequently evolved towards supporting full terminal mobility. Consequently, WiMAX has emerged as one of the most prominent 4G technologies for use in mobile communication, and is capable of supporting an entire range of services from voice to broadband data on top of IP protocol.
There are various phases of a WiMAX network (NSP) search. The end user typically requires a NSP search when the user wants to locate a WiMAX operator (a NSP) to make a subscription in order to be able to enter the network and obtain IP connectivity. The phases in the NSP search are as follows:
1. The terminal (also referred to as a mobile station) searches the frequencies for base stations.
2. Once a base station is found, the terminal identifies the NAP to which the base station belongs. If a full BS ID is included in each frame, the NAP can be identified from the first received frame. However, if a “truncated” BS ID is used by the base station then the full NAP ID is available only in the DCD message (see step 3) and the terminal may thus need to wait to receive the DCD.
3. If NSP connections from the found NAP are not yet known (NSP connections are the same for all base stations of the same NAP), the terminal waits for the base station to broadcast parameters needed for communications (namely DCD and UCD messages). The base station is required to broadcast these messages at least once every 10 seconds.
4. After the DCD and UCD are received, the terminal carries out ranging to the BS in order to adjust the terminal's transmit power and timing to correct values.
5. Upon successful ranging, the terminal initiates capability negotiations. At this point, the terminal is able to query which NSPs are reachable through the NAP. NSP names (that can be displayed for the end user) can be received at this phase.
The foregoing steps are repeated until NSPs for all found NAPs are discovered.
The phases of WiMAX network entry are as follows. Once the end user has subscribed to a service from one of the WiMAX operators (NSP), the terminal is enabled to enter the network based on settings provisioned by the operator. The settings include authentication credentials, priorities for NAPs, a set of frequencies where to look first for the NAPs, and so forth. The terminal then automatically selects a NAP to be used when entry to the network is ordered. The phases are:
1. The terminal searches the set of frequencies for base stations.
2. Once a base station is found, the NAP of the base station is discovered. The NAP is compared against provisioned settings in order to determine whether it can be used for making the connection to the network. Note that in case the “truncated” BS ID is used by the base station, the terminal may have to wait for the DCD message (see step 3)
3. Upon finding a suitable NAP for connection, the terminal waits for the base station to broadcast parameters needed for communication (namely DCD and UCD messages). As was noted above, the base station is required to broadcast this information at least once every 10 seconds.
4. Once the parameters are received capability negotiations are carried out.
5. Capability negotiation is followed by the authentication phase where the subscriber is identified and authenticated to the network
6. Upon successful authentication, the terminal registers to the network.
7. Service flows, which can be used for IP data transfer, are created.
8. The terminal then acquires IP connectivity.
As may be appreciated, the terminal having to wait for DCD and UCD messages slows down both network entry and the NSP search (and also the NAP discovery phase if the “truncated” BS ID is used). If the usage model is such that network is entered only when some application requires IP connectivity, the speed of network search and entry are important at least with regard to the user experience.